1. Field of the Invention
The present invention relates to a video encoding apparatus, a video decoding apparatus, a video encoding method, a video decoding method, and a computer program.
2. Description of the Related Art
Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG, “Text of ISO/IEC 14496-10 Advanced Video Coding,” July 2004, discloses a standard method for video compression which allows an inter-frame prediction to be performed. With such an inter-frame prediction, a region having a pattern similar to that of an encoding target region is detected from an image which has already been encoded, and the pixel values of the region thus detected are used as the predicted values of the encoding target region. In the following description, the processing for obtaining the prediction error that occurs in an inter-frame prediction will be referred to as “motion compensation”. Also, a spatial vector that indicates the offset from an encoding target region to a similar region which has already been encoded will be referred to as an “MV (Motion Vector)”.
With the method disclosed in Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG, in a similar region detection operation (motion estimation operation), pixel values at intermediate positions (fractional position accuracy) are also generated by an interpolation operation in addition to the pixel values at integer sampling positions (integer position accuracy), and the pixel values thus generated by the interpolation operation can also be used as predicted values. The technique disclosed in Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG provides an inter-frame prediction with quarter-pixel precision.
Also, a method (method using an adaptive interpolation filter) has been proposed in Thomas Wedi, “Adaptive Interpolation Filters and High-Resolution Displacements for Video Coding,” IEEE Trans. on Circuits and Systems for Video Technology, Vol. 16, No. 4, April 2006, in which processing is performed on a video pattern or the like in an adaptive manner, which is to be applied to interpolation processing (processing using interpolation filter coefficients) used in an operation for performing motion estimation with fractional pixel accuracy. Such a technique described in Thomas Wedi provides improved encoding performance as compared with the technique described in the aforementioned Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG.